title: Flexibility and torsional behaviour of rotary nickel-titanium PathFile, RaCe ISO 10, Scout RaCe and stainless steel K-File hand instruments.
abstract: OBJECTIVE
  To assess and compare the flexibility and torsional resistance of PathFile, RaCe ISO 10 and Scout RaCe instruments in relation to stainless steel K-File hand instruments.
  
  
  METHODS
  Rotary PathFile (sizes 13, 16 and 19; .02 taper), Race ISO 10 (size 10; 0.02, 0.04 and 0.06 tapers), Scout RaCe (sizes 10, 15 and 20; 0.02 taper) and hand K-File (sizes 10, 15 and 20; 0.02 taper) instruments were evaluated. Alloy chemical composition, phases present and transformation temperatures were determined for the NiTi instruments. For all instruments, diameters at each millimetre from the tip as well as cross-sectional areas at 3 mm from the tip were measured based on ANSI/ADA Specification No. 101 using image analysis software. Resistance to bending and torsional resistance were determined according to specification ISO 3630-1. Vickers microhardness measurements were also taken in all instruments to assess their strength. Data were analysed using analysis of variance (α = 0.05).
  
  
  RESULTS
  The alloys used in the manufacture of the three types of NiTi instruments had approximately the same chemical composition, but the PathFile instruments had a higher Af transformation temperature and contained a small amount of B19' martensite. All instruments had diameter values within the standard tolerance. The bending and torsional resistance values were significantly increased relative to the instrument diameter and cross-sectional area.
  
  
  CONCLUSIONS
  PathFile instruments were the most flexible and the least torque resistant, whilst the stainless steel instruments were the least flexible although they were more torque resistant than the NiTi instruments.
authors.affiliation: Department of Restoration Dentistry, Faculty of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: R K L
authors.initials: RK
authors.lastname: Nakagawa
authors.forename: J L
authors.initials: JL
authors.lastname: Alves
authors.forename: V T L
authors.initials: VT
authors.lastname: Buono
authors.forename: M G A
authors.initials: MG
authors.lastname: Bahia
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D003762:Dental Instruments; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D013052:Spectrometry, X-Ray Emission; D013193:Stainless Steel / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*; D019415:Torque
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; C093824:Martensite; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium
keywords: endodontics; flexibility; glide path instruments; rotary NiTi instruments; torsional resistance